Roundhouse cylinders and valve gear

[LnBmad]

Does anyone have drawings of slip eccentric valve gear to operate roundhouse cylinders? Or can someone provide me with the relevant sizes for me to design my own?

[GTB]

Does anyone have drawings of slip eccentric valve gear to operate roundhouse cylinders? Or can someone provide me with the relevant sizes for me to design my own?

Which R/H cylinder type do you have?

Current production cylinders have valve travel of 5/32" and have a steam chest that is square in plan. They are sold as home builder parts and the valve travel is specified, along with other useful info like mounting hole positions, in the cylinder instruction sheet on the R/H website download page.

I'd increase the eccentric throw a little more than the theoretical 5/64", to allow for any slop in the eccentrics and valve gear, especially as they start to wear.

No idea if the valve travel is the same for the older cylinder type with rectangular steam chests, as I don't have any that old.

Graeme

[LnBmad]

I have the older cylinders. According to the paperwork I found out for them they have valve travel of 6.4mm. Thus my offset for the eccentric should be 3.2mm. I'm just trying to establish how much lap there is on the valves now

[GTB]

I have the older cylinders. According to the paperwork I found out for them they have valve travel of 6.4mm. Thus my offset for the eccentric should be 3.2mm. I'm just trying to establish how much lap there is on the valves now

Sounds like very long valve travel by current R/H standards, so it would be a good idea to check it. You won't get that amount of travel from the current valve gears.

R/H may have used lap on their valves back in the days when their locos were slip eccentric and/or the cylinders had larger ports.

Graeme